A Trigger in SQL is a special kind of stored procedure that automatically executes (or fires) when certain events occur on a table or view. Triggers are mainly used for enforcing business rules, auditing, or maintaining data integrity.

? Key Features of Triggers

• Automatic execution: Runs in response to specific data modification events (INSERT, UPDATE, or DELETE).

• Associated with tables or views.

• Can execute before or after the event.

• Can access the old and new data values involved in the operation.

• Helps implement complex validations and audit trails without manual intervention.

Types of Triggers

Basic Syntax (Example: SQL Server)

CREATE TRIGGER trigger_nameON table_nameAFTER INSERT, UPDATE, DELETEASBEGIN    -- Trigger logic hereEND;

Example: Audit Insertions

CREATE TRIGGER trg_AuditInsertON EmployeesAFTER INSERTASBEGIN    INSERT INTO AuditLog (EmployeeID, Action, ActionDate)    SELECT EmployeeID, 'INSERT', GETDATE()    FROM inserted;END;

• inserted is a special table holding newly inserted rows.

Notes

• Triggers can affect performance if complex or poorly designed.

• Use carefully to avoid recursion or unintended side effects.

• Syntax and capabilities vary across database systems (e.g., MySQL, Oracle, SQL Server, PostgreSQL).

If you want, I can provide a trigger example for your specific database or use case!